1. Field of the Invention
This invention relates to fluid control valves, and more particularly, to gate valves designed for use in the oil and gas industry.
2. Description of Related Art
Industrial piping relies upon many types of valves, but by far the most prevalent are gate valves, which are used in applications where it is desired to prevent or allow flow of fluid through piping. Gate valves are particularly useful when minimal flow restriction is desired. Gate valves operate by having a planar member, the gate, which moves in a cavity within the valve. The gate can be translated within the gate valve so that an opening in the gate is in alignment with the flow passageway of the gate valve, an open position in which the gate valve allows fluid to flow through it from one side to the other. However, if the gate is translated to a position so that the opening within the gate is sufficiently out of alignment and unregistered with the flow passageway, a closed position, the flow through the gate is blocked such that fluid does not pass from one side of the gate valve to the other.
One common way of translating the gate within the valve is by manually rotating a hand-wheel. The hand-wheel is typically attached to a threaded area within the gate valve system so that when the wheel turns, it moves a stem attached to the gate and causes the gate to translate linearly within the valve body housing. When the gate reaches one end of its region of motion within the gate valve, it is in the open position; when it reaches the other end, it is in the closed position.
Another way of translating the gate within the valve is through the use of a hydraulic actuation device. With a hydraulic actuation device, hydraulic pressure can be utilized to open and close the gate valve. This is particularly useful where a large amount of force would be needed to open or close the valve, for example, when gates are under relatively high pressure differentials between one side of the valve and the other. Hydraulic and motorized or other electrical actuation devices provide a way to operate the valve where the force required to turn a hand-wheel is too large. These types of actuation devices are desirable where automation is required.
Many times, it is important to provide a way to easily switch between the manually actuation mechanism to a hydraulic, motorized, or other electrical actuation device while retaining the remaining portions of the gate valve. This ability provides tremendous cost savings. For example, a manufacturer is able to fabricate a valve with a manual hand-wheel actuation mechanism and easily switch to a hydraulic actuation mechanism should the market demand for those types of valves increase. Further, being able to switch the actuation means while the gate valve is still in operation allows a user to reduce system downtime.
Often gate valves carry fluids that contain suspended solids. These fine solid particles can clog the gate passageway. In typical gate valves, solid particles in slurries that pass though the valve passageway tend to escape from the flow passageway into the gate cavity where they can concentrate. In the cavities, these solids can pack and in some cases solidify. These solid particles can compress in the ends of the gate passageway such that the amount of particulate matter at the ends prevent the gate from travelling freely in the gate passageway from a completely open to a completely closed position. When this happens, the gate valve may either provide excessive restriction of fluid flow in the open position on be unable to prevent flow in the closed position.
Thus, there is a need in the art for a gate valve system where the actuation means can be replaced without affecting the integrity of the sealed portion of the valve where all the connection to the actuation means are outside of the sealed portions of the gate valve and having a gate and bonnet design that reduces the buildup of particulate matter inside the gate passageway.